1. Field of the Invention
This invention relates to cargo securing systems for immobilizing heavy bulk cargo during transport thereof. More specifically, the invention relates to structures useful in refrigeration trucks and trailers for stabilizing cargo against sliding movement upon the types of channeled or corrugated floors frequently provided in that type of vehicle.
2. Brief Description of the Prior Art
Perishable foodstuffs are usually transported in refrigerated vehicles. The character of this type of cargo has dictated several criteria in the design of the transports by which it is conveyed. Thus, to assure adequate ventilation to prevent localized spoilage and to improve the overall sanitary environment during transport, the floors of trucks and trailers used for such carriage are usually slotted or channeled to allow cool air to circulate freely beneath the cartons or boxes in which the comestibles are contained. It is also desirable that the interior cargo space of trucks and trailers afford minimum opportunity for dirt, grease or debris to accumulate, and constitute a breeding environment for bacteria. Thus, stakewells or pockets or indentations, which might trap, or act as a repository for, these deleterious materials, are reduced to a minimum or eliminated from the interior walls and ceilings of the vehicles as much as possible.
In the transport of cargo requiring refrigeration, one form of containerization which is finding increased usage is socalled combo loading. In this type of packaging, loose products are loaded into very large cartons and these are then supported upon pallets which rest upon the floor of the refrigeration chamber of the transport vehicle. These cartons are heavy and bulky, and when subjected to the random forces engendered by over-the-road transport they tend to shift from one location to another within the truck or trailer.
At times a portion of the total capacity of the transport trailer is not filled with cargo, and there is more space for the cargo to shift about, and to gain momentum in its movement along the floor or deck of the truck or trailer bed. As a consequence, the cartons in which the cargo is packaged are frequently bent or heavily damaged, and the cargo itself is sometimes ruined or rendered less marketable.
Although various systems and devices have been proposed for stabilizing or immobilizing cargo carried in trucks, some of these structures are not entirely satisfactory where refrigerated cargo is being transported over substantial distances. The described problem of eliminating recesses or pockets in order to prevent bacterial growth by obviating sites for accumulation of dirt, grease or the like makes it undesirable to use bars which extend from one side of the truck body to the other, and are anchored at opposite ends in sockets or recesses formed in the truck walls. The same desideratum also places some limitation on straps or flexible members extended around the cartons and/or pallets in order to arrest movement of the cargo, since ultimately such flexible securing elements must be anchored in some way to either the walls, floor or ceiling of the truck, and this again sometimes entails the provision of undesirable sockets, wells or pad eyes to enable such anchoring to be accomplished.
In Deering et al. U.S. Pat. No. 3,602,474, a pallet restraint apparatus is illustrated and described. This apparatus includes a snubbing device or block which is mounted to one side of a cargo pallet by means of a threaded bolt which can be used to draw the snubbing block vertically in relation to the pallet. A portion of the snubbing block projects laterally from the pallet and, as the snubbing block is moved vertically by rotation of the threaded bolt, this portion of the block is brought into frictional engagement with restraint rails mounted in a vehicle to provide guidance and restraint to the pallet and the cargo carried thereon.
In one form of the Deering restraint apparatus, a resilient slipper is placed over a portion of the snubbing block, and by cooperation of an inclined surface formed at one side of the slipper with an inclined surface formed on the snubbing block, the slipper is caused to expand laterally as it undergoes vertical compression during the vertical movement of the snubbing block. This lateral displacement of the resilient slipper, combined with the compressive force exerted thereon to also cause lateral resilient deformation, forces the slipper into firm engagement with a vertical portion of the restraining rail, and thus further enhances the locking function of the restraint apparatus.
The Deering pallet restraint apparatus requires that the snubbing system be built into, and made an integral part of, the pallet, and further requires specific and fixed positioning of certain movable elements of the restraint apparatus in order to engage restraint rails of a particular shape which must be located in the cargo-carrying vehicle at a particular location in relation to the pallets in order for the systems to function effectively. Where the specific dimensional and spatial relationships of restraint rails and the pallets positioned therebetween do not characterize the cargo transport in use, the pallet restraint apparatus provided in the Deering et al. patent cannot be employed. Moreover, the pocket which is formed in the elastomeric slipper utilized in one form of the Deering pallet restraint apparatus also provides a receptacle within which debris can accumulate in the course of a relatively short period of usage of the apparatus.
A different type of anchoring device which provides a direct interlock between the bed of a freight transport vehicle and cargo containers carried therein is the twist lock structure illustrated and described in Baaso U.S. Pat. No. 4,125,077. The twist lock structure here contemplated requires modification of the existing bed of the transport vehicle for its installation.
Sterling U.S. Pat. No. 2,688,289 depicts and describes a cargo tie-down assembly which includes an undercut channel which functions as a keyway to receive a base structure affixed to a tie-down ring. The base structure is rotated in the channel to bring a flange carried on the base structure into locking engagement with the undercuts of the channel, and prevent the ring structure from being pulled out of the channel. The undercut channel provides lateral pockets which are largely enclosed and can become packed with dirt and grime, and then afford a favorable breeding environment for deleterious organisms. Moreover, the Sterling cargo tie-down assembly does not afford good anchoring capability against longitudinal movement along the length of the channel in which the tie-down ring is located, and it is therefore necessary to depend upon elongated straps or flexible elements extended around the cargo and attached to the tie-down ring in order to prevent shifting of the ring and base structure in a direction away from the cargo.
A system which is generally similar to that disclosed in the Sterling patent is described in Bass et al U.S. Pat. No. 3,344,749. The type of interlock provided in the Bass et al structure between the undercut channel and the ring carrying structure can, however, be manipulated to prevent longitudinal sliding movement of the ring structure relative to the channel.
Other patents disclosing devices which employ, in one form or another, undercut channels which are used in conjunction with tie-down devices for preventing the shifting of cargo, are those which are shown in Lautzenhiser et al. U.S. Pat. No. 3,478,995 and Elsner U.S. Pat. No. 2,735,377. In both of these patents, a ring-type structure is anchored in undercut rails or channels, and flexible straps are then used to extend from the rings around the cargo and retain it in position. Yet another patent of the strap ring, undercut channel type is that which is shown in Williams U.S. Pat. No. 2,052,914.
The described previously patented systems are exemplary of various prior art devices which have been utilized for the stabilization of cargo during transport. Some of the structures are quite useful for some forms of containers or pallets employed, and are suitable in certain types of trucks having floors which lend themselves to the required modification entailed in using the structure. Each of the devices, however, either presents structural installation problems, or poses undesirable sanitary conditions in use due to the inclusion of cavities or pockets, which make them less than optimum for use on reefers or refrigerator vehicles. Moreover, where belting or a flexible tie-down element is required as a part of the system in use, securement of the cargo is time-consuming and, in addition, the compressive or squeezing force exerted upon the containers by the straps or other flexible members used sometimes distorts or crushes the cargo containers and may "bruise" or damage the cargo.